Polymerization of chlorophosphazene esters with polyfunctional organic hydroxy compounds

ABSTRACT

1. A LIQUID POLYMERIC PHOSPHAZENE PREPARED BY A PROCESS COMPRISING REACTING A PHOSPHONITRILE CHLORIDE POLYMER HAVING THE GENERAL FORMULA:   -(N=P(-CL)2)N-   IN WHICH N IS AT LEAST 3 WITH A LOW MOLECULAR WEIGHT GLYCOL CONTAINING 1 TO 6 CARBON ATOMS TO FORM A PARTIALLY ESTERIFIED PORDUCT AND FURTHER ESTERIFYING THE PRODUCT WITH ALKYL ALCOHOLS CONTAINING 1 TO 6 CARBON ATOMS, SODIUM ALKOXIDES CONTAINING 1 TO 6 CARBON ATOMS OR ALKYLENE OXIDES CONTAINING 2 TO 6 CARBON ATOMS.

United States Patent 3,840,621 POLYMERIZATION 0F CHLOROPHOSPHAZENEESTERS WITH POLYFUNCTIONAL ORGANIC HYDROXY COMPOUNDS Borivoj RichardFranko-Filipasic Morrisville, Pa., and John Francis Start, Mercerville,N.J., assignors to FMC Corporation, New York, N.Y. No Drawing. FiledMar. 1, 1972, Ser. No. 230,954 Int. Cl. C07f 9/24 U.S. Cl. 260-927 NClaims ABSTRACT OF THE DISCLOSURE New phosphonitrilic esters containinga substantial amount of cyclic structures, dimerized, oligomerized, orpolymerized, are prepared by esterification of a phosphonitrilicchloride polymer with ethylene glycol.

This invention relates to a new class of phosphonitrilic esterscontaining a substantial amount of cyclic structures dimerized oroligomerized by esterification of a phosphonitrilic chloride withethylene glycol.

It is desirable, for'many textile purposes, to provide cellulose fibersand yarns having greatly decreased flammability. In the manufacture ofrayon by the viscose method, rayon has been made permanently flame-retardant by dispersing in the rayon a flame-retardant amount of asubstantially water-insoluble, liquid, phosphonitrilic polymer asdisclosed by Godfrey in US. Pats. Nos. 3,455,713, 3,505,087, and3,532,526 issued July 15, 1969, Apr. 7, 1970, and Oct. 6, 1970. Thesephosphonitrilic polymers are conventionally made by esterifying apredominately trimeric chlorophosphazene (phosphonitrilic chloridepolymer). A predominately cyclic chlorophosphazene can be made bybringing into contact elemental chlorine, phosphorus trichloride andammonium chloride in an inert solvent at reflux temperatures asdescribed in U.S. Pats. NOS. 3,359,080 and 3,462,247

issued .Dec. 19, 1967, and Aug. 19, 1969, respectively.

Although the Godfrey compositions do not seriously degrade rayon fiberproperties, it is. always desirable to have more effective flameretardants allowing attainment of adequate flame retardance at a loweradditive level with a consequent lowered impairment of physicalproperties of the rayon fibers and a decrease in cost. Recently, it hasbeen discovered that phosphonitrilates of increased viscosity areimproved flame retardants for rayon. Thus, it is highly desirable toprovide processes for making phosphonitrilates havingenhancedflame-retardant effects in rayon.

In accordance with the present invention, there are provided newsubstantially water-insoluble, polymeric phosphonitrilates containing asubstantial amount of cyclic structures dirnerized or polymerized byesterification of a phosphonitrilic chloride polymer with ethylenegylcol.

These dimerized or polymerized phosphonitrilic esters, also termedphosphonitrilates, are fluids of unusually high viscosity and molecularweights and they are exceptionally useful for making permanentlyflame-retarded rayon. These phosphonitrilates are used to flame retardregenerated cellulose in amounts of l25% by weight based on thecellulose. One such hosphonitrilate has a structure represented as:

in which R is a lower alkyl or alkene radical containing 1-6 carbonatoms.

Phosphonitrilate esters are made by first preparing a chlorophosphazeneor phosphonitrilic chloride by a conventional process as described inUS. Pats. Nos. 3,359,080 and 3,462,247 issued Dec. 19, 1967, and Aug.19, 1969, respectively, which comprises bringing in contact elementalchlorine, phosphorus trichloride and ammonium chloride in an inertsolvent at reflux temperature, the ammonium chloride being present atany time during the reaction in a proportion at least equal molar withthe phosphorus trichloride. The chlorophosphazenes are reacted with alow molecular Weight glycol, such as ethylene glycol, propylene glycol,and the like, which is used as a coupling agent. This results incoupling and esterification of the chlorophosphazenes to produce estersof greatly increased viscosity. Where desired, esterification is notcomplete. Conventional esterification procedures can be used to completethe esterification, such as reaction of the residual chloride atoms withan alcohol, alkoxide or alkylene oxides.

Conventional chlorophosphazenes can be cross-linked with lower glycolscontaining 1 to 6 carbon atoms with ethylene and propylene glycol beingpreferred. Reaction with the glycol connects the chlorophosphazenemolecules. When complete esterification does not result from reactionwith the glycols, alkyl alcohols, sodium alkoxide and alkylene oxidescan be used to complete esterification. The alkyl and alkenyl portionsare generally those containing 1 to 6 carbon atoms, and include suchradicals as ethyl, Z-chloroethyl, methyl, n-propyl, isopropyl, bntyl,isobutyl, amyl, isoarnyl, hexyl, allyl and crotyl groups. Amines such astriethyl amine to form amine hydrochloride are used for ease in handlingand processing and are not part of the invention.

The phosphonitrilic chloride polymer used in this invention is a cyclictrimer, tetramer or higher cyclic polymer, or a linear polymer and ispreferably employed as a mixture of these isomers based on economy andsimilar performance to the pure compound.

The lowest possible temperatures conducive to efilcient processing areused. Temperatures of to 120 can be used. However, it is preferred touse temperatures of to 105 C. with the lower temperatures of 90-100 C.being preferred.

These esterifications are rapid and exothermic. The time of the reactionis controlled by the ability of the reaction vessel to removve theexothermic heat when there is a moderate rate of diluent reflux.

The fluids, diluents or solvents used in the process of this inventionare inert to the reaction mass, capable of reflux at temperatures overC. and easily removed by distillation. Aromatic solvents such as tolueneor paraflinic solvents such as octane are preferred.

The reactant ratios are carefully controlled in order to achieve thedesired physical characteristics in the fluid product. The preferredreactant ratios are 5 to 10 moles of phosphonitrilic chloride per moleof glycol. The most preferred reactant ratio is about 8 moles ofphosphonitrilic chloride per mole of glycol.

The following examples further illustrate this invention. Allproportions in the specification and in the examples are by weightunless otherwise noted.

EXAMPLE 1 Increasing the molecular weights and consequently theviscosities of the flame-retardant fluids by coupling or cross-linkingwith ethylene glycol either during or previous to propyl ester formationis demonstrated. Essentially pure trimer of phosphonitrilic chloride,(PNCl was prepared (by fractional crystallization) and reacted asfollows: To a solution of 11.6 gms. (0.33 mole) of (PNCl in 50 ml. oftoluene was charged slowly with agitation 1.03 gms. (0.0166 mole) ofethylene glycol dissolved in 6 gms. (0.0595 mole) of triethylamine. Thesolution was agitated for 30 minutes at 100 and cooled slowly. The solidamine hydrochloride was removed by filtration and the filtrate wascharged to sodium propoxide in toluene at reflux. The ester was obtainedby waterwashing the crude mixture and concentrating the dried organiclayer. The desired compound Was the ethylene glycol ester ofbis-pentapropoxycyclotriphosphazatriene. The product was obtained in78.8% yield as a viscous liquid, refractive index 1.46-96- at 22, acidnumber 11.5, viscosity 6075; centistokes at 25. The molecular weight byvapor phase osmometry was 1088 (920.8 calculated for the bis ester).Elemental analysis, nitrogen=9.l4% found, 9.12% calculated;phosphorus=20.86 found, 20.18 calculated; chlorine=0.3l% found,calculated.

EXAMPLE 2 The preparation of Example 1 was repeated with cyclic, hexanesoluble (PNCl mixture, 25 gms.; ethylene glycol, 1.55 gms.;triethylamine, 10 ml.; all in 100 ml. of toluene solution. Isolation ofthe glycol ester and further complete esterification with sodiumpropoxide yielded 75% of a viscous fluid refractive index 1.4700 at 23,a molecular weight of 982, and a viscosity of 3285; centistokes at 25 C.

EXAMPLE 3 Cyclic, hexane soluble phosphonitrilic chloride, principally(PNCl 25 gms.; ethylene glycol, 1.7 gms.; triethylamine, 10 gms.; all in100 ml. of toluene Were utilized. The ester was isolated and esterifiedfurther and completely with sodium propoxide. There was obtained aviscous fluid in 85% yield, refractive index 1.4703 at 24", a molecularWeight of 751 and a viscosity of 720 centistokes at 25 EXAMPLE 4 Toillustrate the use of ethylene glycol during the formation of propylesters, a solution of 78 ml. of n-propanol and 3.6 gms. of ethyleneglycol were charged to a mixture of 18 gms. molten sodium metaldispersed in 225 ml. of toluene at 102 to 105. The mixture was refluxedwith agitation for 30 minutes to insure complete reaction. A solution of38.3 gms. of cyclic phosphonitrilic chloride, principally (PNCl mixturein toluene solution was added slowly to the refluxing mixture. Heatingwas continued for 5 /2 hours during which time samples were withdrawnevery 30 minutes and analyzed for unreacted chloride. When the chloridelevel was 0.1%, the reaction mixture was cooled and washed with tapwater to dissolve the salts. The organic layer was separated, dried, andconcentrated in vacua. There was Obtained a viscous fluid of thefollowing physical properties:

Average molecular weight 1100 Viscosity (centistokes at 25) 2175Refractive index at 24 1.4674

Elemental analyses follow:

Calculated for Found R=propyl C 39. 43 44. 17 Ft 7. 41 8. 65 N 8. 87 8.58 P 20. 11 18. 98 Cl 0. 08 0. 00

EXAMPLE 5 were injected into the viscose stream at the desired ratebased on the weight of the cellulose in the viscose and the viscosemixture passed through a high shear blender. This provided a viscosehaving the flame retardant dispersed therein as fine liquid particles offrom 1 to 10 microns in size.

Viscoses prepared as described above and containing deliberately variedamounts of the phosphorus-containing flame-retardant compounds were spuninto conventional aqueous acid spin baths comprising 9.8 wt. percentsulfuric acid, 3.0 wt. percent zinc sulfate and 17.5 wt. percent sodiumsulfate at a bath temperature of 50 C. The yarn was wet stretched about35% of its original length. Yarns having a denier of 240 and 40filaments were processed by passing them through a series of bathsincluding Water wash, desulfurization, bleach, bleach acid, antichlor,and soft finish bath. The yarns were dried, transferred to packages, andfinally knit into circular knit fabrics. The regenerated cellulose yarnsprepared in this manner were made up of individual filaments having fineliquid flameretardant particles locked in the cellulose matrix.

Assays of the flame retardant in the fabrics were made by determiningthe phosphorus content of the neat flame retardants and the fabrics.

The table sets forth the weight amount of flame retardant in theconditioned fabric, the weight amount of phosphorus in the dryregenerated cellulose fabric, and the percent of flame retardantretained in the finished fabric compared to the amount originallyinjected into the viscose. The amount of phosphorus in the dry fabricwas used to calculate the amount of flame retardant present in theconditioned fabric. The control flame retardant was that described inthe Example of US. 3,455,713 and consisted of a liquid mixture ofdi-n-propyl phosphonitrilate polymers including about 65% trimer, 15tetramer, between about 15 and 20% of higher cyclic polymers and lessthan about 5% of linear polymers.

Flammability testing was made by employing the 1) Limited Oxygen Index(LOI) method and (2) the Vertical Strip Test AATCC34-1969.

The LOI test is made by supporting a 3" x 8" conditioned fabric samplein a U-shaped frame which is mounted in a cylindrical open chamber.Controlled mixtures of oxygen and nitrogen gases are admitted into thebase of the chamber and allowed to displace the normal atmosphere. Whenan equilibrium atmosphere in the chamber is obtained, the fabric sampleis ignited with a butane gas flame by contacting the flame to the topedge of the fabric. If the fabric fails to ignite, the oxygen ratio ofthe atmosphere is increased to a level where the flame will justpr0pagate. Conversely, if the fabric ignites and the flame propagates,the oxygen ratio of the atmosphere is reduced to a level where flamepropagation is virtually zero. The LOI is the minimum percentageconcentration of the oxygen atmosphere in which the test fabric willignite and permit flame propagation. A control rayon fabric has an LOIof 18.5.

The vertical strip test is made by supporting a 3" x 10" fabric samplein a U-shaped frame which exposes 2" x 10" fabric. The sample and frameis supported vertically in a draft-free chamber with the open end of thefabric frame pointed down. Ignition of the fabric is made with a TirrellBurner fueled with butane. A 1%" long flame is aligned to the base ofthe fabric so that of the flame bites into the fabric. Flame contacttime is for (a) 3 seconds and (b) 12 seconds. Data are obtained to showthe length of the char and the time of after flame.

The table also sets forth the results of the above describedfiammability tests carried out on the fabric samples. It should be bornein mind that the tests were made using knitted fabrics of relativelylight construction. The vertical flame-retardant test results are usefulfor a relative appraisal of the fabrics tested as this test is greatlyaffected by fabric weight. In the vertical test, five samples aretested, the average char length must be less than 7 inches to pass andone char of 10 inches fails the test.

5 6 The limited oxygen test data have greater relevance to yl, ethyl,propyl, isopropyl, butyl, isobutyl, amyl, isoamyl the flammability ofnormal apparel Weight fabrics since f hexyl fadicalsh d d d f b 4. Theproduct of claim 1 in WhlCh the alkyl portion t e 8 oxygen m Ices arenot epen em on a no of the alkylene oxides may be ethyl, propyl,isopropyl, weight. butyl, isobutyl, amyl, isoamyl or hexyl radicals.

TABLE Vertical Flame Test 3 sec. 12 see. Limited Fabric Percent FROxygen Char After Char After, sample in condi- Percent Index length,flame, length, flame Flame retardant (FR) number tioned fabric P Testin? see. in. sec.

Example4 1 5.0 1.17 25.3 10.0 (F) 15.6 10.0 (F) 4.2

2 9.2 1.91 204 10.0 (F) 14.2 6.9 NAF 3 11.7 2.43 204 10.0 (F) 14.6 5.8NAF Control 1 5.0 0.98 23.8 10.0 18.0 10.0 7

2 9.9 2.11 25.7 10.0 17.0 9.0 NAIF-5.0 3 11.0 2. 30 24.7 10.0 17.2 9.0NAF-77 4 14.1 2.00 25.3 9.0 13.0 5.6 NAF 5 16.9 3.50 0 3.0 NAF-45 5.2NAF 6 21.0 4.30 20 3 1.9 NAF 5.2 NAF Over 7 inches fails in the threesecond test. No after flame. (F)=Failed. What is claimed is: 5. Theproduct of claim 4 having a viscosity of 20 to 1. A liquid polymericphosphazene prepared by a proc- 5000 poises at 20 C. ess comprisingreacting a phosphom'trilic chloride polymer having the general formula:References Cited UNITED STATES PATENTS 2,909,446 10/1959 Redfarn et a1.117-138 3,453,236 7/1969 Klender 260927 NX -f7 FOREIGN PATENTS 1,381,02310/1964 France 260927 N 162,532 10/ 1964 Russia 260927 N in which n isat least 3 with a low molecular weight glycol REFERENCES containing 1 to6 carbon atoms to form a partially ester- Phosphonltl'lllc chemlstry, C& P ified product and further esterifying the product with PP- 1 alkylalcohols containing 1 to 6 carbon atoms, sodium 40 Matuszko: Indexchemlcus, 22, 69578 alkoxides containin 1 to 6 carbon atoms or alk leneoxides containing 2 6 carbon atoms y LORRAINE A. WEINBERGER, PrimaryExaminer 2. The product of claim 1 in which the glycol is ethyl- R. L.RAYMOND, Assistant Examiner ene glycol or propylene glycol.

3. The product of claim 1 in which the alkyl portion US. Cl. X.R. of thealkyl alcohols and sodium alkoxides may be meth- 106168; 260973

1. A LIQUID POLYMERIC PHOSPHAZENE PREPARED BY A PROCESS COMPRISINGREACTING A PHOSPHONITRILE CHLORIDE POLYMER HAVING THE GENERAL FORMULA: